Browsing by Author "Barrow, KD"

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    Immobilization of dendrimers on Si-C linked carboxylic acid-terminated monolayers on silicon(111)
    (Elsevier, 2006-12-05) Bocking, T; Wong, ELS; James, M; Watson, JA; Brown, CL; Chilcott, TC; Barrow, KD; Coster, HGL
    Poly(amidoamine) dendrimers were attached to activated undecanoic acid monolayers, covalently linked to smooth silicon surfaces via Si-C bonds. The resulting ultra-thin dendrimer films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XR) and atomic force microscopy (AFM). XPS results suggested amide bond formation between the dendrimer and the surface carboxylic acid groups. XR yielded thicknesses of 10 angstrom for the alkyl region of the undecanoic acid monolayer and 12 A for the dendrimer layer, considerably smaller than the diameter of these spherical macromolecules in solution. This was consistent with AFM images showing collapsed dendrimers on the surface. It was concluded that the deformation arose from a large number of amine groups on the surface of each dendrimer reacting efficiently with the activated surface, whereby the dendrimers can deform to fill voids while spreading over the activated surface to form a homogeneous macromolecular layer. © 2006, Elsevier Ltd.
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    Novel approach for enhancing the catalytic efficiency of a protease at low temperature: reduction in substrate inhibition by chemical modification.
    (Wiley-Blackwell, 2009-07-01) Siddiqui, KS; Parkin, DM; Curmi, PMG; De Francisci, D; Poljak, A; Barrow, KD; Noble, MH; Trewhella, J; Cavicchioli, R
    The alkaline protease, savinase was chemically modified to enhance the productivity of the enzyme at low temperatures on a complex polymeric protein (azocasein) substrate. At 5 and 15 degrees C, savinase modified with ficol or dextran hydrolyzed fivefold more azocasein than the unmodified savinase. Kinetic studies showed that the catalytic improvements are associated with changes in uncompetitive substrate inhibition with K-i values of modified savinases sixfold higher than the unmodified savinase. Modeling of small-angle scattering data indicates that two substrate molecules bind on opposing sides of the enzyme. The combined kinetic and structural data indicate that the polysaccharide modifier sterically blocks the allosteric site and reduces substrate inhibition. In contrast to the properties of cold-active enzymes that generally manifest as low activation enthalpy and high flexibility, this study shows that increased activity and productivity at low temperature can be achieved by reducing uncompetitive substrate inhibition, and that this can be achieved using chemical modification with an enzyme in a commercial enzyme-formulation. Biotechnol. Bioeng. 2009;103: 676-686. © 2009, Wiley-Blackwell.